1. Field of the Invention
The invention relates to a tank system, in particular a fuel tank system having a splash pot and a filling level sensor, and to a method for controlling and operating such a tank system.
2. Related Art
It has already been proposed, for example, in German Application no. 196 10 154.9) to provide, within the main tank of a motor vehicle, an additional or reserve volume which is always filled up as a priority and which is automatically released by means of a switchable valve, as required (lowering of the filling level of the main tank below a predetermined minimum value). In order to improve the driver's information on the fuel supply available, simultaneously with the release of the reserve a signal indicating this operation and/or an accurately indicating or high-definition addition indication of the residual fuel quantity is activated. The vehicle driver can consequently estimate the remaining range of his vehicle more accurately. Use is made, in this case, of the fact that the geometry of the additional volume is simpler than that of present-day main tanks, since, with a view to optimum space utilization, these sometimes have a highly angular shape and therefore make it difficult to detect and indicate the filling level accurately.
The reserve supply is released into the main tank or into a splash pot, preferably directly on the suction side of the fuel pump. The additional volume is filled preferably directly from the inflow pipe (also tank filler neck).
It is normally located directly above the tank bottom and is always kept full. For refilling during operation, for example, suction jet pumps are used, which are operated by forward or return fuel streams and convey a volume flow constantly out of the main tank into the splash pot. There are also solutions with two-stage fuel pumps, the first stage of which feeds out of the main tank into the splash pot and the second stage of which then delivers from the splash pot to the carburetor or injection pump.
Excess quantities run over the upper edge of the splash pot back into the main tank. Suitable means (splash pot plates, labyrinth systems) prevent the splash pot from being emptied unintentionally, even when the vehicle undergoes high accelerations or decelerations. In the known system, admittedly, the changeover of the reserve release valve is controlled by a filling level limit switch arranged in the splash pot itself. Although it must be assumed that the splash pot will always be full if there is a sufficient supply of fuel in the main tank, in this configuration the possibility cannot be ruled out that, in the event of a merely temporary lack of fuel in the splash pot, the reserve volume is released prematurely and is then used up by the time the next refueling occurs.
Furthermore, a measuring device for tanks in motor vehicles is known, which possesses a main sensor arranged in a main tank and a secondary sensor for the filling level arranged in a secondary tank, as described in German Patent no. 32 24 919 A1). The volume present in the secondary tank serves as a reserve and is indicated. However, the indicated reserve is dependent on a filling level signal from the main sensor in the main tank. Since only the one measuring point is present in the main tank, the main sensor delivers signals which, depending on driving situations, are different from the actual filling level. The reserve indicator therefore also gives situations which differ from the actual filling level.